Economic pressure seems to be the West's main weapon against Russia. Although a Russian official did warn yesterday that his country will respond in kind, tit-for-tat, to any economic sanctions imposed by the U.S. Leaders of European Union are meeting today in Brussels to discuss toughening sanctions, which could cause pain in their own economies.

We're joined now by Juan Zarate. He's a former assistant secretary of the Treasury for Terrorist Financing and Financial Crimes. And he also wrote the book "Treasury's War."

Good morning.

JOHN ZARATE: Good morning, Renee.

MONTAGNE: Now, you know as much as anyone about how sanctions work. And so, just briefly, what did you make of earlier this week when the U.S. and E.U. targeted a small group of President Putin's circle? I mean these were limited sanctions that some of those in Kremlin just laughed off.

JUAN ZARATE: Right, Renee. But what I saw in those actions was the opening salvo of potential actions to isolate Russian individuals, entities and companies. It was really the underlying authorities that was signed by the president on March 17 and the previous executive order of March 6 that opened the spigot to potentially isolate Russian banks, arms merchants and others.

And so even though the list was relatively short, it was the opening step, I think, in a financial campaign. But we do have a challenge of overstating the immediate effects of these efforts and I think the administration has to calibrate how they talk about the potential effects of these initial steps.

MONTAGNE: Well, first of all, do you think that the spigot will be open? That is to say the sort of Iran-like heavy duty pressure on banks and other institutions that underpin Russia's economy.

ZARATE: Well, Russia's a different case study, obviously. We could certainly turn the financial pressure and tools that we've put on countries like Iran or rogues like North Korea against Russia, but that's a major policy decision. That would be turning a country that in many ways we've tried to make a partner in the global anti-money laundering system into a target for financial and economic isolation.

We certainly have the tools to do it. I mean we could begin to identify Russian banks that are underwriting not just activities in the Ukraine that are destabilizing, but also underwriting weapons transfers to President Assad in Syria, companies that are evading sanctions, maybe playing footsie with Iran, individuals that are tied to organized crime, law enforcement investigations tied to Russian businesses and networks, asset hunts, so that we have a full suite of sanctions and tools that we could put on the table. The key question, though, is do we turn Russia and Russian entities, in particular banks and businesses, into the targets of that isolation? And that's difficult when we know the Russian bear can bite back.

MONTAGNE: Yeah, that's a huge question. And, of course, isn't the key to sanctions to get the target country to bend to one's demands? And what are the goals of sanctions in this case if Russia is not giving Crimea back, which is pretty clear?

ZARATE: No. Absolutely right. And I think we have to realistic about what sanctions and financial pressure can do, especially in the immediate term. I've said often, these are not a silver bullet. They're not going to roll back the troops from Crimea. They're not going to, you know, pull down the Russian flags flying over the cities in Crimea at this point.

So you have to see what the effects are. And I think long term, what you can do are impose real costs on Russian economic interests and prestige. You want these measures, if you're going to deploy them, to punish and deter, but you obviously don't want to aggravate the situation and you don't want to incur countermeasures that are going to be detrimental to Western interests. I think that's the reality.

And one of the concerns, Renee, is that Russia, at the end of the day, could serve as a refuge for other financial rogues. Russia has been relatively cooperative in this space. They serve as the president of the Financial Action Task Force, the international body that focuses on this. They're hosting a meeting in June of anti-money laundering experts. And so do you put all that at risk by making Russia a key target of these financial measures?

That's a core question that, frankly, has not yet been answered.

MONTAGNE: Well, thank you for joining us again. Lots to talk about in the coming days.

ZARATE: Absolutely. Thank you, Renee.

MONTAGNE: Juan Zarate is a senior advisor at the Center For Strategic and International Studies. Transcript provided by NPR, Copyright NPR.